Analytical apparatus and instrumentation for on-line measurement of volatile organic compounds in fluids

ABSTRACT

A device and method for the continuous on-line or discrete off-line concentration and measurement of organic compound contaminants in a fluid sample stream is disclosed, in which an adsorbent trap means, which may be a tube of metal packed with an adsorbent composition such as a carbon-based composition, is used to adsorb the organic compound contaminants, while venting out permanent gases, such as CO, CO 2 , N 2 , O 2 , NO 2 , SO 2 , CH 4 , and H 2  O. The adsorbent trap means is capable of rapid heating and cooling, and when a pulse of electrical energy or microwave energy is applied thereto, the adsorbed organic compound contaminants are rapidly desorbed therefrom; after which they are carried to a detector means for measuring the organic compound contaminants. Embodiments are included in which gas chromatography (GC) is not employed. A sampling valve may also be used to cause the sample stream to enter and be retained in a sample retention element of the sampling valve, after which the valve may be repositioned to cause the measured portion of the sample stream to be ejected from the sample retention element and be carried to the adsorbent trap means. A computer may also be used together with a power supply and a recording device in order to control all of the operations and measurements of the device and method, so that they are carried out in accordance with a predetermined schedule, or in response to the dictates of said sample measurements, or both.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation-in-part of application Ser. No.08/475,701, filed Jun. 7, 1995, now abandoned; which is acontinuation-in-part of application Ser. No. 07/076,414 filed on Jun.14, 1993, and now U.S. Pat. No. 5,435,169.

FIELD OF THE INVENTION

The present invention relates to methods and devices for continuouson-line and discrete off-line monitoring of organic compoundcontaminants in fluid streams. The present invention is particularlyconcerned with monitoring concentrations of such contaminants in termsof recognized categories based on different analytical techniques: totalorganic carbon (TOC), non-methane organic carbon (NMOC), and volatileorganic compounds (VOCs). The fluid streams in which such organiccompound contaminants can be found, and in which their presence must bedetected and their concentrations measured, are, e.g., those fluidstreams emitted from industrial and commercial stacks, those dischargedas effluents from air toxic control devices and as waste water fromplants, and those present in drinking water sources.

BACKGROUND OF THE INVENTION

Organic compound contaminants, especially volatile and volatilizableorganic compounds (VOCs) in the environment may be hazardous to publichealth even at very low concentrations, since many of the VOCs aretoxic, mutagenic, and/or carcinogenic, such as aromatic and halogenatedcompounds. Organic compound contaminants which are "volatile", as thatterm is used in the present invention, are those which have a relativelyhigh vapor pressure and can be found in vapor form at relatively lowtemperatures. However, there is also included within the definition of"volatile organic compounds" (VOCs), as that term is used in the presentinvention, organic compounds which are "volatilizable", i.e., capable ofbeing made volatile. Such volatilizable organic compounds areparticularly those which may vaporize under the conditions ofconcentration and detection to be found during the methods of thepresent invention. The measurement of VOCs in air has become a veryimportant goal. Conventional VOCs monitoring methods involve collectinga sample at the site and transporting it to the laboratory for analysis.While these methods are quite accurate, they cannot be utilized forcontinuous on-line analysis to provide information on a real-time basisas required for effective pollution control and for meeting regulatoryrequirements. A discussion of such methods, and of the state of the artrelating to them, can be found in U.S. Pat. No. 5,435,169, which isincorporated herein by reference in its entirety.

In accordance with the present invention, analytical apparatus andinstrumentation is provided which can be used in various aspects ofcontinuous on-line measurement of organic compound contaminants, andwhich can also be used off-line for isolated, i.e., discretemeasurements which may be single instances or repetitive occurrences.The objective of the analytical apparatus and instrumentation isthree-fold. The organic compound contaminants are to be concentrated tofacilitate detection of low concentrations; interfering species such asCO₂ and H₂ O are to be eliminated; and then the trapped organic compoundcontaminants are to be injected into the detector. A variety of detectorsystems may be used with this analytical approach, e.g., non-methaneorganic carbon analysis (NMOC), total organic carbon analysis (TOC),mass spectrometry (MS), infrared spectroscopy (FIR), or any othersuitable detection system. Systems of this type can be used on-line tomonitor emissions from industrial stacks, vents and similar sites fromwhich emissions originate.

Total Organic and Non-Methane Organic Carbon Analysis--Total organiccarbon is a measure of total carbon emissions in organic form, i.e., thetotal carbon content less that derived from the permanent gases such asCO₂ and CO. Non-methane organic carbon (NMOC) is another category oforganic compound contaminant measurement frequently used in addition tototal organic carbon, and is a measure of the total organic carboncontent of a sample, except that coming from methane. In non-methaneorganic carbon analysis, methane, CH₄, is treated as a permanent gas,although it is not treated as a permanent gas in the other analyses.

In the mid-1970's, EPA Standard Method 25 was developed for quantifyingNMOC emissions from stationary sources. In that method, gas samples arecollected and sent to a lab for analysis. In a conventional non-methaneorganic carbon analyzer, one milliliter of gas sample is introduced intoa separation column a through a gas sampling valve. The column is usedto separate VOCs from permanent gases such as CO₂, CH₄ and CO. After thegases elute from the column, i.e., a CO₂ peak appears, the column isbackflushed into the detector system and all of the organics are thenmeasured together as one peak.

The detection system comprises an oxidation unit, a reduction unit and aflame ionization detector (FID). The reason for converting all of theorganic compounds to CH₄ is that different compounds have differentresponse factors in FID, and in this manner a response directlyproportional to the number of carbon atoms is obtained.

The use of column separation in conventional NMOC analysis posessignificant problems especially when the sample contains large amountsof moisture and the concentration of CO₂ is above 8% by volume of thesample. Another major problem is that the detection limits are not lowenough, as a result of the fact that the injection volume must belimited in order to obtain good separation in the column. Anotherdrawback of this method is that it cannot be used for continuous on-linemonitoring. Other total organic carbon analysis methods are also usedwhere, instead of reducing the CO₂ to methane, the CO₂ itself ismeasured using infrared or other suitable detection means.

Continuous On-Line FID, MS and FTIR--At present on-line analysis is doneusing a flame ionization detector (FID) for total hydrocarbon analysis.Similarly, the mass spectrometer (MS) and the Fourier Transform.Infrared Spectrophotometer (FTIR) are used for on-line VOCs monitoring.In the case of both the FID and the MS, the sample is introduceddirectly into the detector. No sample concentration is used, and thusthe detection limits are quite high. However, H₂ O, CO and CQ₂, whichare always present in environmental emissions, interfere in theanalysis. In the case of the FTIR, the absorbance spectra is measured ina flow cell, or else a long path FTIR is used in which the IR beam isreflected across the emission source. Here also, the presence of H₂ O,CO and CO₂ can also interfere with the analysis.

Monitoring VOCs in Water--Most conventional VOCs monitoring is done byusing the purge and trap method. Typically, the sample is collected inthe field and then transported to the laboratory. On-line purge and trapsystems have also been developed for semi-continuous monitoring.

SUMMARY OF THE INVENTION

In accordance with the present invention, devices and methods aredisclosed for the continuous, substantially real-time, monitoring ofvery low level concentrations, i.e., levels below parts per million byvolume (ppm), and even levels below parts per billion by volume (ppb),of organic compound contaminants for environmental and chemical process,monitoring and control purposes. The device has general utility ineffectively continuous on-line monitoring using different detectiondevices such as those for non-methane organic carbon (NMOC) and totalorganic carbon (TOC); specific devices, e.g., the mass spectrometer (MS)and the Fournier Transform Infrared Spectrophotometer (FTIR); totalhydrocarbon analysis using a Flame Ionization Detector (FID), GasChromatograph (GC) associated detectors; and other detector means, e.g.,the Electrolytic Conductivity Detector (ELCD), Electron Capture Detector(ECD), Thermionic Ionization Detector (TID), Nitrogen PhosphorousDetector (NPD), Flame Photometric Detector (FPD), and ThermalConductivity Detector (TCD), and so forth.

The key operating feature of the method of the present invention is theuse of an adsorbent trap means for the organic compound contaminants,which may be based, e.g., on the differential adsorbent capacity ofcompositions such as activated carbon, on the differential temperatureeffects of cryogenic processes, etc., to capture and retain the organiccompound contaminants while the interfering and background species,e.g., H₂ O, CO₂, CO, etc., are permitted to pass through. The organiccompound contaminants are then released quickly from the adsorbent trapmeans, preferably through a rapid desorption achieved by the heating ofthe adsorbent trap means. Following desorption, the sample is injectedinto one of the detector means identified above, e.g., by the use of aninert carrier gas.

The devices and methods of the present invention are useful for thedetection and measurement of organic compound contaminants in fluidsample streams. The fluid stream may be either gaseous, e.g., air, orliquid, e.g., water. Where the sample stream is gaseous, it is preferredthat the detector means be other than gas chromatography (GC). Gaschromatography is, properly, a means for separating the components of asample, and a detector means associated therewith may be used to "read"the results, i.e., to physically identify the separated components. Ithas been found that by using the adsorbent trap means of the presentinvention and rapid desorption of the organic compound contaminantstherefrom, that it is not necessary to employ gas chromatographyseparation, as required in the methods of the prior art. A gaschromatographic separation step may be included, however, and ispreferred in the methods of the present invention where the fluid samplestream is water or a liquid effluent containing or suspected ofcontaining organic compound contaminants.

In U.S. Pat. No. 5,435,169, the disclosure of which is incorporatedherein by reference in its entirety, a method and correspondingapparatus for the continuous, on-line GC analysis of VOCs is disclosed,which involves the collection of VOCs in a concentrator element, and theseparation of the VOCs from the permanent gases, followed by theintroduction of the sample to a gas chromatography (GC) column. Theconcentrator element is an adsorbent trap means containing at least oneadsorbent that is able to separate the organics by adsorption, whileventing the permanent gases. The concentrator is purged by desorptionand the desorbed gases are then injected into the GC and associateddetector. This process is performed rapidly and frequently in order toachieve effectively continuous on-line monitoring. This process and thecorresponding apparatus are outlined in U.S. Pat. No. 5,435,169 withrespect to VOCs and the injection of the concentrated material into aGC. However, the need for greater analytic simplicity, together withextended functioning of the adsorbent trap means for separation of amore specific array of interfering materials, has led to itsimplementation with additional detector means such as FID, MS, FTIR,ELCD, ECD, TID, NPD, FPD, and TCD, and additional applications such asthe monitoring of NMOC and TOC concentrations. The resulting improvedmethod and corresponding apparatus for continuous on-line use of thepresent invention will now be described.

Application in NMOC, FID, MS and FTIR Monitoring--The method of thepresent invention is quite different from the conventional on-line NMOC,TOC, FID, MS or FTIR analysis. The sample containing the organiccompound contaminants is passed directly through an adsorbent trap,which selectively retains the volatile organics while allowing the othergases, e.g., CO, CO₂, O₂, N₂, SO₂, and NO₂, as well as moisture, to passthrough. Then the trap is rapidly heated by electrical, microwave orother heating sources to desorb the organic compound contaminants intothe detection system. The adsorbent trap is designed to heat and coolvery rapidly, so that injections can be made very frequently, e.g.,every few seconds to every few minutes. Substantially continuousanalysis is possible by repeating this cycle frequently. The trap servesthree purposes: (1) trapping and concentrating the organic compoundcontaminants; (2) separating moisture and the permanent and other gasesfrom the sample; and (3) injecting the organic compound contaminantsinto the detector instrument. Measurements at very low concentrationlevels are possible because the pollutants are concentrated within thetrap, which can be used by itself or in conjunction with other injectiondevices, especially a conventional sample valve.

Monitoring Organic Compound Contaminants in Water--The method and deviceof the present invention can also be used for the monitoring of organiccompound contaminants in water. The aqueous sample containing theorganic compound contaminants passes through a membrane module in whichthe organic compound contaminants selectively migrate across themembrane into an inert gas stream. The organic compound contaminants aretrapped and concentrated by an adsorbent trap means. The retainedorganic compound contaminants are desorbed from the adsorbent trap meansby an electrically generated heat pulse which also serves as aninjection for GC separation. As an alternative to membrane separation,the separation can be accomplished by sparging. The subsequent analysiscan be done by any detection system, e.g., FID, TOC, MS, FTIR, or GC.

More specifically, the present invention comprises a method for thecontinuous or discrete monitoring of concentrations at trace levels aslow as fractional parts per billion, of TOC/NMOC as well as VOCs,pollutant levels in a fluid stream. The method comprises the steps ofcollecting at least one sample of the organic compound contaminantsusing collecting means, from the fluid stream and concentrating saidcollected samples using concentration means. At predetermined timeperiods, the concentrated, collected samples are desorbed from theconcentration means, using desorption means; and the desorbed,concentrated, collected samples are injected into a detector. The stepsare repeated rapidly on a regular and continuing basis in order toprovide substantially real time, effectively continuous on-linemonitoring. Detectors specifically include FTIR, TOC/NMOC analyzers, GCdetectors, e.g., FID, NPD, FPD, TID, TCD, and ECD, mass spectrometers(MS), as well as any sensor in general. In the case of water, theorganic compound contaminants are first separated, e.g., by membraneseparation or sparging, after which the analysis may be done by any ofthe above-mentioned detectors or GC-associated detectors.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of the NMOC monitoring system of thepresent invention.

FIG. 2 is a schematic depiction of injection in the sequential valvemode (SVM) for a device of the present invention.

FIG. 3 is a schematic diagram of injection in the on-line adsorbent trappurge mode (OLAT-P).

FIGS. 4A and 4B are a schematic depiction of injection in the on-lineadsorbent trap back-flush mode (OLAT-BF).

FIG. 5 illustrates the detector output obtained from the monitoring ofsimulated stack gas by the SVM injector and NMOC analyzer. The adsorbenttrap means selectively retains organic compounds, while the permanentgases, e.g., CO₂, CO, H₂ O, O₂, and N₂, pass through. First, a largepeak is seen, which is due to CO₂, CH₄, and CO. Then, the adsorbent trapwas desorbed by a pulse of current to obtain the NMOC peak. Adsorbenttrap means pulses occurred every four minutes, at points I₁, I₂, I₃,etc. The flow rate of the sample stream was 6.0 ml/min. The simulatedstack gas composition was as follows: benzene, 1 ppm; trichloroethylene,1 ppm; toluene, 1 ppm; ethylbenzene, 1 ppm; oxygen, 10.9%; carbondioxide, 9.27%; carbon monoxide, 75 ppm; sulfur dioxide 164 ppm; and thebalance nitrogen.

FIG. 6 illustrates a detector output obtained from the monitoring ofsimulated stack gas by the OLAT-BF system. First, the sample passedthrough the adsorbent trap means, where the organic compoundcontaminants were retained while the permanent gases passed through.Then, the valve was turned to the injection mode, the adsorbent trap washeated by a pulse of current in the presence of a stream of He carriergas, and the organic compound contaminants were injected into thedetector. A small peak for CO₂ and CH₄ is followed by a large peak forNMOC. The composition of the simulated stack gas was the same as in FIG.5.

FIG. 7 is a graph showing a calibration curve for use in the NMOC systemusing SVM and OLAT-BF injection.

FIG. 8 is a graph showing the results from monitoring a catalyticincinerator. The inlet and outlet concentrations are plotted againsteach other.

FIG. 9 is a graph showing the effect of moisture content on the NMOCsystem response.

FIG. 10 is a schematic diagram for on-line monitoring of organiccompound contaminants using a FID.

FIG. 11 is a graph showing the response of the FID using the adsorbenttrap means to alternately trap and desorb organic compound contaminantsas a concentration pulse.

FIG. 12 is a graph comparing the calibration curves for the FID detectorwith and without the adsorbent trap means pulses.

FIG. 13 illustrates continuous on-line mass spectrometric analysis of asample stream containing toluene, in the presence of large quantities ofCO₂ and H₂ O.

FIG. 14 is the mass spectrum of point "a" in FIG. 13, showing mainlypermanent gases such as H₂ O, N₂, and CO₂.

FIG. 15 is the mass spectrum at point "b" in FIG. 13, showing theresults of desorption of the adsorbent trap means, where toluene, mass91, is the main product.

FIG. 16 is a schematic diagram of a water monitoring system.

FIG. 17 is a chromatogram generated by injecting a water samplecontaining ppb levels of organic compound contaminants in the water.

These and other objects, features and advantages of the presentinvention will become more evident from the following discussion anddrawings.

DETAILED DESCRIPTION OF THE INVENTION

There will now be described in detail the analytical apparatus andinstrumentation necessary to achieve the continuous monitoring of NMOClevels. This description and the principles underlying it are fullyapplicable to continuous monitoring using FID, MS, FTIR, and otherdetectors. A schematic diagram of the continuous monitoring system, asapplied to NMOC monitoring, is shown in FIG. 1. The preferred gas samplevalve is a six-port air actuated valve with a digit interface, e.g., onefrom Valco Instruments Co. Inc., College Station, Tex. A small diameteradsorbent trap, sometimes referred to as the microtrap, is made, e.g.,by packing a 0.5 mm i.d., 6- to 9-inch long tube with adsorbents such asCarbotrap®, a carbon based adsorbent. Any known adsorbent having thedesired affinity for organic molecules will be suitable for use with thedevices and methods of the present invention. Examples of differentclasses of suitable adsorbents are the carbon based adsorbents,including activated carbons such as activated charcoal; molecularsieves; and the polymer-based adsorbents, including Tenax®. Variouscombinations of two or more of these adsorbent materials may also beused.

The adsorbent trap means is sometimes referred to herein as the on-lineadsorbent trap means, or OLAT. The adsorbent trap means is connected toa variable power supply, and can be desorbed using an electrical pulseof short duration. The electrical pulse is used to cause heating of theadsorbent trap means, which in turn leads to desorption of the adsorbedspecies. A computer-controlled electrical switch is used to regulate theintervals between pulses and the duration of each pulse. Directresistive heating of a metal-based adsorbent trap means is a preferredembodiment of the present invention. Other heating means for achievingthe desired desorption will be within the skill of the artisan tocontrive, e.g., external heating means may be used, such as a heatingtape wrapped about the adsorbent trap or a heating element applied in asimilar fashion, or a device for subjecting the adsorbent trap means tobombardment by microwaves of sufficient strength and duration to resultin heating of the adsorbent trap means and the adsorbed organic compoundcontaminants therein. The adsorbent trap means is configured with asample valve so that the organic compound contaminants are first caughtby the trap, while the permanent gases such as CO₂, CO and H₂ O arevented out of the trap. An inert carrier gas such as helium (He) is thenused as a carrier for the desorbed organic compound contaminants, tomove them from the adsorbent trap means into the detection system.

The oxidation reactor used in the NMOC detector system is, e.g., a1/4-inch stainless steel tubing packed with Chrome Alumina, about 4inches long. This reactor is put in a furnace, e.g., one from Lindberg,Watertown, Wis. The reduction unit is, e.g., a 1/4-inch o.d. quartz tubepacked with 10% nickel nitrate on Chromosorb G AW 100/120 from Varian,Calif. The typical operating temperature for the oxidation unit andreduction unit are about 650° C. and about 400° C., respectively. AnFID, e.g., one from Hewlett Packard is used in the study. In anotherembodiment of the present invention, total organic carbon (TOC)concentration can be determined by eliminating the reduction catalyststep in the NMOC process, along with the FID detector means, andsubstituting for the latter a suitable CO₂ detector means.

The system is operated by passing the gas to be analyzed directlythrough the sample injection system. Periodically, injections of sampleare made by heating the adsorbent trap means, and for each desorption, apeak is seen at the instrument of the detection system. Continuousmonitoring is achieved by making a series of injections at fixedintervals of from every few seconds to every few minutes, and obtaininga corresponding series of detector responses. Chromatograms illustratingsuch continuous monitoring are depicted in FIG. 5 and FIG. 6.

The devices of the present invention can be configured in several ways,several of which are illustrated in FIGS. 1, 2, 3 and 4 The adsorbenttrap means can be connected directly to the detector, as in the on-lineadsorbent trap purge mode (OLAT-P) shown in FIG. 3; or as in the on-lineadsorbent trap backflush mode (OLAT-BF) shown in FIG. 4. Otherconfigurations may be used, for example that illustrated in FIG. 2,which is a sequential valve adsorbent trap means mode (SVM). In the SVMmode, one or more valve injections are made to effectively inject alarge gas volume into the adsorbent trap means, which captures theorganic compound contaminants. The adsorbent trap means is then heatedto desorb the Organic compound contaminants into the detector. In thismode, CO₂, CO, H₂ O and other permanent and related gases, first passthrough the adsorbent trap means, after which desorption of the organiccompound contaminants occurs, preferably in the presence of an inertgas. In this way, these various species of gas which would otherwiseinterfere with the detection of the organic compound contaminants, areeffectively separated from the organic compound contaminants.

Another mode of operation of the system is to install the on-lineadsorbent trap means (OLAT) with one or more valves such that the airsample passes directly through the adsorbent trap. In this mode, theanalytes first pass through the trap, and H₂ O, CO₂, and CO are removed.The adsorbent trap means is desorbed to inject the organic compoundcontaminants into the detection system. In the OLAT-P mode, twoautomatic three-way valves can be used, and are configured so that airsample first passes through the adsorbent trap and is vented out. Then,both valves are turned so as to be configured to pass helium, He,through the adsorbent trap; after which the adsorbent trap is desorbedand the organic compound contaminants thereby displaced are carried bythe helium and injected into the appropriate detector. Other valveconfigurations employing, e.g., six or ten ports, may also be used, solong as they further the basic objective of the method, i.e., toeliminate the permanent gases such as CO, CO₂ and H₂ O and therebyseparate them from the organic compound contaminants, and thereafterdesorb the organic compound contaminants from the adsorbent trap andinject them into a detector means by way of a carrier gas such ashelium. For example, it is possible to configure the system so that theadsorbent trap is backflushed into the NMOC detector, as shown in FIG.4A. In this OLAT-BF mode a six port valve system is used. First, thesample passes through the adsorbent trap means, where the organiccompound contaminants are retained while the permanent gases passthrough. Then, the valve is switched, and a flow of He connects theadsorbent trap to the detector. The adsorbent trap is heated by a pulseof electrical current in order to desorb the organic compoundcontaminants and inject them into the detector. The desorption iscarried out in the backflush mode. Backflush desorption may also beaccomplished by the use of 2 three-way valves, one on either side of theabsorbent trap, as shown in FIG. 4B. Using a flow direction fordesorption which is the reverse of that used for sampling allows theleast mobile compounds, which are separated and held in the proximateareas of the adsorbent trap, to be desorbed without being forced throughthe length of the trap, thus facilitating their desorption andincreasing sensitivity of detection. This also becomes important withrespect to the most mobile compounds, which are separated and held inthe distal areas of the adsorbent trap, and are much more capable oftraveling the length of the trap during desorption. These considerationsplay an especially important role where the adsorbent trap contains twomore adsorbent materials with different adsorbent capacities, or whereseveral different samples having different contaminants are introducedto the adsorbent trap sequentially. These situations substantiallyincrease the likelihood that the adsorbed contaminants will be"layered", i.e., physically located in different portions of theadsorbent trap.

Both of the modes of operation described above produce linearcalibrations curves as shown in FIG. 7. A study was carried out in whichthe NMOC system was used to monitor the inlet and outlet of a catalyticincinerator. The results of this study are illustrated in FIG. 8, whichshows that as the inlet concentration increased, the outletconcentration also increased.

A major problem with conventional NMOC analysis using EPA Method 25 isthat in the presence of moisture, column separation is difficult. In theanalytical apparatus and instrumentation utilized in the presentinvention, the adsorbents which are utilized are made of hydrophobicmaterials which do not retain moisture, but do capture the organiccompound contaminants. Thus, the moisture is eliminated from the systemand does not create problems in detection of the organic compoundcontaminants. As illustrated in FIG. 9, the instrument response is notaffected by even large amounts of moisture. The same type of samplingsystem can be used in other applications. For example, the reductionunit in the NMOC system can be eliminated and a CO₂ detector means canbe used to replace the FID detector means.

Applications Utilizing FID and MS--The above-described operational modessuch as SVM, OLAT-P, and OLAT-BF, can also be used in on-line FID or MSanalysis. For example, as illustrated in FIG. 10, the adsorbent trapmeans is directly connected to the FID means. As was the case with NMOC,it has been found that a series of peaks are obtained which correspondto a series of thermal pulses transmitted to the adsorbent trap means,and this advantage of the device is clearly shown in FIG. 11, as well asin FIG. 12, where calibration curves for on-line monitoring with andwithout the adsorbent trap means are illustrated. From this data it canbe clearly seen that the detector response utilizing the adsorbent trapmeans is much higher than the response without the adsorbent trap means,and that the slope of the calibration curve is also higher. Any of theconfigurations illustrated in FIGS. 2-4 can also be used.

The above-described sampling system can also be utilized with a MSdetector, and the adsorbent trap means performs in the same manner thefunctions of sample concentration, the elimination of interfering gasspecies, and the injection of the organic compound contaminants into thedetector instrument. The MS generated response is illustrated in FIG.13. One of the problems encountered with conventional on-line massspectrometry is that H₂ O, CO₂, CO, etc. present in the emission gasesinterfere in the ionization process. The adsorbent trap arrangementsshown in FIGS. 1-4 can be used to eliminate these potentiallyinterfering gases. The advantage of this system of the present inventionin monitoring by MS is illustrated in FIG. 13. The experiment whoseresults are shown in the graph of this figure, was done with ppb leveltoluene in the presence of large quantities of CO₂, H₂ O, etc. At pointB, where the peak corresponding to injection from the adsorbent trap isseen, a large peak for mass 91 (toluene) is readily observable. At pointA, only background gases are present. When the same sample of toluene atthe same concentration was introduced directly into the MS detectormeans, toluene could not even be detected in the presence of such largequantities of permanent gases. It can be seen that the intensity ofpeaks using the adsorbent trap means based injector are much higher. Theratio of organic compound contaminants to CO₂ is also much higher whenthe adsorbent trap means based injector is used, demonstrating that theadsorbent trap means injector was able to successfully remove the CO₂.

Water Analysis--Where water analysis is being carried out, the organiccompound contaminants have to be removed from the water prior toanalysis. A membrane may be used for this purpose, as is illustrated inFIG. 16. An eluant fluid, such as pure water, e.g., deionized water,flows continuously through the membrane module which contains one ormore hollow fiber membranes. Other designs are also suitable, e.g., oneutilizing flat membrane sheets. The water sample containing the organiccompound contaminants is injected through an injection valve, e.g., aconventional six-port valve. The eluant fluid carries the sample intothe membrane. As the water passes through the membrane, the organiccompound contaminants permeate the membrane and are retained in the trapuntil they are injected into the detector or a GC. It is also possibleto simply use an adsorbent trap means connected directly to the GCcolumn, or to use any of the configurations of FIGS. 1-4. In particular,it is possible to use the configuration of FIG. 3 with 2 three-wayvalves, one on either side of the adsorbent trap, and to carry out thedesorption in a backflush mode. This configuration is illustrated inFIG. 4B. The advantages of such backflush desorption have already beendescribed further above. Such backflushing procedures are well known inthe art. See, e.g., "Simultaneously Monitor Saturated and UnsaturatedC2-C6 Hydrocarbons in Air Samples" Sample Handling Bulletin 850A,Supelco Separation Technologies, 1991; and Kebbekus and Mitra,Environmental Analytical Chemistry, pp. 8-13, 14, 1996, which areincorporated herein by reference in their entirety. By utilizing theseprocedures, it is possible to measure the contaminants in a series ofwater samples retrieved from one or more separate locations. This can bedone quickly and efficiently. The adsorbent trap again serves thefunction of concentrating the organic compound contaminants, separatingthem from the permanent gases, and injecting them into a gaschromatograph. In this experiment a composite membrane with a siliconecoating was used for separating the organic compound contaminants. Avariety of other polymer materials can be used, which are non-porous,e.g., silicone-based polymers, or porous, e.g., polypropylene. Compositemembranes consisting of a porous core structure having coated thereon anon-porous film, e.g., silicone, can also be used. Single sampleanalysis is done by making one injection. Continuous analysis can bedone by making a series of injections. This system is an alternate topurge and trap analysis. Typical results obtained using this system areshown in FIG. 15. Here a GC is used to separate the different organiccompound contaminants from each other. Instead of a GC, other detectormeans such as TOC/NMOC, MS, FTIR, etc. can also be used.

There are a number of ways in which the analytical apparatus andinstrumentation of the present invention differ from those specificallydescribed in U.S. Pat. No. 5,435,169. For example, the methods in thepatent focus their attention on chromatographic separation, and rely ona gas chromatograph in most instances. In the present invention, theorganic compound contaminants are introduced directly to the detectorswithout chromatographic separation, but the separation of CO₂, H₂ O andCH₄ from the organic compound contaminants has become a critical part ofthe present process. In gas chromatography, the injection has to beabrupt, e.g., less than 1 sec, in order to obtain high resolution. Inthe present process, by contrast, the injection can take place overseveral seconds. Where water analysis is being carried out, the patentprocess can only be utilized for continuous monitoring, while thepresent process can be used either for continuous monitoring, or foranalyzing numerous, different samples. The present process also differsin that it relates to determinations of NMOC, direct MS, and direct FIDand FTIR detection, which are not emphasized by the processes of thepatent.

What is claimed is:
 1. A device for the continuous measurement ofNon-Methane Organic Carbons (NMOCs) in a fluid sample stream withoutchromatographic separation, comprisinga sampling and concentrationsystem connecting said sample stream to an NMOC detector; said samplingand concentration system comprising one or more multi-port valves tofluidly connecting said sample stream to an adsorbent trap means; saidadsorbent trap means being capable of rapid heating and cooling, andcontaining at least one adsorbent composition which adsorbs the NMOCs insaid sample stream; said multi-port valve means fluidly connected tosaid trap means which allows the venting out of CO, CO₂, O₂, N₂, SO₂,NO₂, H₂ O and other gases in said sample stream so as to concentratesaid NMOCs in said trap means; desorption means associated with saidadsorbent trap means whereby said adsorbed NMOCs are rapidly desorbedtherefrom and injected into said NMOC detector; fluid carrier meansconnecting said sample stream to said adsorbent trap means, and saiddetector means; means whereby the one or more multi-port valves operatesimultaneously so as to pass said carrier means through the absorbenttrap into said detector means so as to carry said desorbed NMOCs fromsaid adsorbent trap means into said detector means as a concentratedpulse.
 2. A device according to claim 1 wherein the multi-port valvemeans comprises a gas sampling valve which makes an injection onto thetrap means which retains the NMOC and vents said CO, CO₂, O₂, N₂, SO₂,NO₂, H₂ O and other gases, prior to desorption of the NMOC into saiddetector.
 3. A device according to claim 1 wherein the multi-port valvemeans comprises two three port valves operating simultaneously with thetrap means fluidly connected therebetween.
 4. A device according toclaim 1 wherein the multi-port valve means passes the sample through thetrap means while venting said CO, CO₂, O₂, N₂, SO₂, NO₂, H₂ O and othergases, and further, the valves are switched such that the flow directionof carrier fluid through the trap is reverse of that of the sample toallow backflushing of the trap means during desorption into saiddetector means.
 5. A device according to claim 1 where the process isrepeated continuously and repetitively, so as to provide near real-timemonitoring of said fluid sample.
 6. A device according to claim 1wherein the said detector means comprises an oxidation means to convertorganic to carbon dioxide which is then measured, or further convertedto methane using reduction means connected in series with the oxidationmeans, and measuring the thus-produced methane using FID.
 7. A deviceaccording to claim 6 wherein the oxidation and reduction means arecatalytic and/or thermal.
 8. A device according to claim 6 wherein thecarbon dioxide is measured by an infrared spectrophotometer.